1. Field of the Invention
This invention relates in general to apparatus for cutting a hole in a workpiece and more particularly to a tool used in conjunction with a standard 1/2" industrial quality drill which quickly and efficiently cuts a hole in metal for electrical conduit.
2. Description of the Prior Art
Several well-known tools can be used to cut holes in a workpiece. For use in wood applications, it is conventional to use a special hole cutting bit with a standard drill. A door knob hole, for example, can be cut using this type of bit and a standard industrial quality drill. In metal applications, a well-known device termed a "Uni-bit" can be used again in conjunction with a standard drill. Alternatively depending on the hole size, a metal punch may be used in certain applications.
Disadvantages of the above-mentioned devices exist which limit their utility. If the object in a given application is to quickly and efficiently drill a smooth, true, concentric hole in a metal workpiece such as a panel for disposing electrical conduit therein, the previously mentioned conventional devices have several shortcomings. Smoothness of the drilled hole is occasionally compromised due to premature breakthrough of the hole cutting bit. Devices which rely on a pushing force by the operator have problems in certain applications since manually maintaining a constant pressure on the cutting bit during the entire operation is difficult, and when a constant pressure on the cutting bit is not maintained, a less than smooth hole may result. Also, conventional cutting teeth tend to prematurely break through the metal even if a constant pressure is maintained in certain metal applications which causes a rough and less than concentric hole. The present invention overcomes these disadvantages and provides a hole cutting tool which efficiently and precisely cuts a hole in metal and can be adapted to accommodate a wide range of hole sizes.